| 摘要 |
Apparatus for receiving and demodulating call related information, e.g., Caller ID information, includes an audio codec (104) placed on the line side and powered by current drawn from the telephone line. The audio codec includes a 1<st> order SIGMA / DELTA A/D converter (140) to digitize the signal from the telephone line with SIGMA / DELTA modulation. The 1<st> order SIGMA / DELTA A/D converter may be a scaleable component capable of alternative operation in a 2<nd> order. The SIGMA / DELTA encoded digitized signal is digitally processed by a DSP (110) including an amplifier module, a digital filter, a limit/slice module, and an FSK decoder to receive and output the call related information. Placement of the audio codec (104) on the line side and the scaleable SIGMA / DELTA A/D converter (140) provides significantly reduced power requirements for the audio codec, thus allowing operation from power derived from the telephone line. In another embodiment, to further reduce power consumption of the audio codec, the 1<st> order SIGMA / DELTA A/D converter is sampled at a slower rate than is conventional, e.g., by first dividing or otherwise providing a slower sampling clock. <IMAGE> |
